doc: updated documentation site

[fredbi]

• domains: defined "async" domain as a better fit than "condition" for all async testing assertions
• maintainers: documented how to add a go version guard assertion; fixed codegen tests & go.work undue upgrade
• other minor documentation additions

Change type

Please select: 🆕 New feature or enhancement|🔧 Bug fix'|📃 Documentation update

Short description

Fixes

Full description

Checklist

• I have signed all my commits with my name and email (see DCO. This does not require a PGP-signed commit
• I have rebased and squashed my work, so only one commit remains
• I have added tests to cover my changes.
• I have properly enriched go doc comments in code.
• I have properly documented any breaking change.

[codecov]

Codecov Report

❌ Patch coverage is 96.39889% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.70%. Comparing base (9ba6261) to head (13a4b4a).
⚠️ Report is 1 commits behind head on master.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
internal/assertions/async.go	96.75%	10 Missing ⚠️
codegen/internal/scanner/buildtags.go	96.07%	2 Missing ⚠️
codegen/internal/scanner/scanner.go	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #166      +/-   ##
==========================================
+ Coverage   93.65%   93.70%   +0.04%     
==========================================
  Files         102      103       +1     
  Lines       13884    13937      +53     
==========================================
+ Hits        13003    13059      +56     
+ Misses        874      871       -3     
  Partials        7        7              

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